Carburetor for an Internal Combustion Engine

Field of the Invention

The present invention relates to "Carburetor for an Internal Combustion Engine" and more particularly to prevention of contaminants such as dust and related particles entry through the drain device to the float bowl of the carburetor.

Background of the invention

Carburetor is used to blend air and fuel for an internal combustion engine. The conventional carburetors have a float bowl which holds the fuel. The said float bowl is generally provided with a drain tube which permits excess fuel to be safely drained out from the carburetor. The said drain tube assembly that is inserted into the float bowl has a top end which opens inside the said float bowl and the other lower end opens to the atmosphere for facilitating and providing pressure balance in the drain passage.

This excess fuel draining arrangement which is provided in the conventional carburetors has, one end of the drain tube opened to atmosphere, thereby it allows the air to pass through it. The said passage of air leads to the possibility of introducing additional contaminants such as dust into the carburetor float bowl and fuel through the said drain tube. The introduction of the contaminants into the float bowl of the carburetor contaminates the fuel in the carburetor, and thus affecting the engine performance as well as the life of the engine components.

In addition to the above said problem the dust particles which enter into the carburetor float bowl unit cogs the airflow in the drain path whereby the draining of excess fuel from the carburetor will not be effected, and will cause unwanted carburetion and engine operation conditions. Hence there is a need for a carburetor having a excess fuel draining system which wail prevent the entry of contaminants such as dust and related components into the carburetor unit.

When the same carburetor construction is used for gaseous fuel, the float bowl of the said carburetor remains empty since it does not have to hold any fuel. In the above mentioned case because of the pressure difference air is sucked from atmosphere through the drain tube lower end. The dust and related components are also sucked in this process and contaminates the gas entering the engine and thereby leading to unwanted engine performance.

Further, there are carburetors which are provided with independent air filter at the end of the said drain tube. This provision increases the size of the carburetor system as well as the manufacturing cost. Hence there is a need for a carburetor drain system which will prevent the entry of contaminants and does not result in increasing the size as well as the cost of the carburetor system.

Summary of the Invention

The present invention relates to an excess fuel drain system for a carburetor of an internal combustion engine which prevents the contaminants entry through the drain tube passage into fuel in the carburetor float bowl and to the engine combustion chamber.

The main object of the present invention is to provide a carburetor for an internal combustion engine with an excess fuel drain system which prevents the contaminants entry through the drain tube into fuel in the carburetor float bowl and thus to the engine combustion chamber.

Another object of the present invention is to provide an excess fuel drain system capable of preventing the dust entry into carburetor float bowl through the drain tube which does not result in increase in the size of the carburetor.

Yet another object of the present invention is to provide an excess fuel drain system capable of preventing the dust entry into carburetor bowl through the drain tube which makes the carburetor system cost effective-Further another object of the present invention Is to provide an excess fuel drain system capable of preventing the dust entry into carburetor bowl through the drain tube, which will also work for both gaseous and non gaseous fuel.

Yet another object of the present invention is to make the carburetor system work efficiently without affecting engine performance.

Further scope of applicability of the present invention wail become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while Indicating preferred; embodiments of the invention, are given by way of illustration only, since various;

changes and modifications within the spirit and scope of the invention will
become apparent to those skilled in the art from this detailed description.

Brief Description of the Drawing

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present Invention, and wherein
Figure.1 illustrates a conventional motorcycle.
Figure. 2 is front view of a conventional carburetor.
Figure ,3 is cross sectional view of a conventional float bowl.
Figure.4 (a) is a cross sectional view of float bowl with no or less fuel as per first
embodiment of the present Invention.
Figure.4 (b) is a cross sectional view of float bowl with fuel excess than the
predetermined level as per first embodiment of the present invention.
Figure. 5 is showing the top, sectional and perspective view of the float. Figure. 6 is the inside top view of the carburetor float bowl. Detailed Description of the Invention

Embodiments of the present invention now be described with reference to the accompanying drawings, in the following description, "front", "rear", "upper", "lower", "right", "left" and "bottom" represent directions viewed from the perspective of the vehicle rider.

The present Invention relates to the carburetor for an internal combustion engine, for the purpose of illustration only it will illustrated with the help of a two wheezier motorcycle.
First the whole structure of the vehicle will be roughly described. With reference to Figure. 1, a motorcycle comprises of a frame (101), front fork (102) attached to a pivot tube (103) of the vehicle frame, a front wheel (104) attached to these front furs (102), a handle bar (105) connected to the front forks (102), a fuel tank (106) attached so as to straddle an upper part of the vehicle frame, a seat (107) attached to the upper rear portion of the vehicle frame, an engine unit (108) attached to the lower front section of the vehicle frame, a swing arm (109) attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown in the drawing) from the vehicle frame and a rear wheel (110) attached to a rear end of swing arm (109). The intake system of the engine comprises of a carburetor (117), intake duct and an air cleaner. The exhaust system of the engine comprises of exhaust pipe and a muffler. The motorcycle is also provided with a side cover (111) for covering a side section of the vehicle frame, a seat cover for covering a rear section of the vehicle frame below the seat, a front fender (112) for covering an upper part of the front wheel (104), an a rear fender (113) for covering an upper part of the rear wheel (110). The drive from the engine (108) is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly.

With reference to Figure.2 which represents a carburetor comprising a main body (201) Including an intake (202) and outlet (203) passageways. The said intake (202) is for the air to enter the passageway and the said outlet (203) is from which air fuel mixture goes to the engine. A throttle valve inside 204 is located at the bottom of the carburetor. The float bowl is used as a reservoir for holding fuel which is supplied from a fuel inlet line. The fuel is drawn from the float bowl (205) to the main body passageway to mix with the air coming from intake (202) which passes into the combustion chamber of an internal combustion engine through outlet (203).

With reference to Figure.3 which represents a conventional carburetor float bowl (205) with a drain tube (301). The said drain tube (301) has one end (303) open to the atmosphere and the other top end (302) opens inside the float bowl (205). Normally it is necessary to drain fuel from the carburetor of an internal combustion engine when the fuel level inside the said float bowl (205) exceeds the predetermined level and to accomplish this draining, the carburetor has a drainage outlet (303) at the lowermost point of the said float bowl and the top end (302) of the said drain tube (301) is opened for facilitating and providing a pressure balance In the drain passage of the carburetor. When there is no fuel in the said float bowl (205) or when the same float bowl (205) construction is used for gaseous fuel, air is sucked through the said drain tube (301) from the atmosphere. Since the said float bowl (205) Is empty for the gaseous fuel due to pressure difference, air will be sucked through the drain tube when the gaseous fuel travels through the main body passageway (201), This atmospheric air entry through the said drain tube (301) brings the dust and contaminants, which settles down In the float bowl and gets mixed with the gaseous fuel moving in the passageway of the main body (201) of the carburetor to the internal combustion engine, thereby affecting the engine performance.

With reference to Figure.4 ( a and b ), which Is a cross sectional view of the carburetor float bowl according to the first embodiment of the present Invention. The said carburetor is provided with a drain tube (402) having a drain hole (403) towards the top end of the said drain tube (402) which is opened inside the said float bowl (402).

A foam float like member (404) preferably made of up polymer resin is provided around the said drain tube (402). The said foam float (404) is mounted co axially with the said drain tube (402). Normally the float (404) closes the drain hole (403) (as shown in Figure 4 a), when there is no excess fuel or no fuel (as in the case of gaseous fuel ) in the said float bowl (404). The said foam float (404) around the drain tube shifts downward thereby closing the said drain hole (403). Closure of the drain hole (403) prevents entry of any kind of dust or contaminants through drain tube (402) to the float bowl (401).

Further when there is excess fuel or fuel above the predetermined level in the said float bowl (401) (as shown in Figure 4 b), the said foam float (404) being less dense than the fuel, gets lifted up and thereby opens the said drain hole (403) in the said drain tube (402). The opening of the said drain hole (403) in the said drain tube (402) facilitates draining of excess fuel.

The special arrangement of the said foam float (404) in the drain system which allows closing of the drain hole in drain tube when there is no excess fuel or no fuel in the bowl, restricts the atmospheric air entry into the said drain tube (402), and thus prevents the dust entry into carburetor float bowl and the engine combustion chamber.

The said drain tube (402) top end (405) is closed by the top surface of the said float bowl (401). The said drain tube (402) allows the foam float (404) to guide and travel along the drain tube surface.

With referring to Figure 5 the foam float (404) is preferably made in D shape, A projection or rib like member (406) from the bottom of the float bowl (401) is provided to support the flat surface of the D shaped float (404). The orientation of the said drain hole (403) in the said drain tube (402) is made perpendicular to the above said projection axis. The window or opening (407) provided at the top in the said float (404) is perpendicular to the flat surface of the float (404) thereby making both the said window (407) of the float (404) and drain hole (403) of the said drain tube (402) to align with each other. Figure 6 illustrates the inside top view of the said float bowl (401) showing the D shaped foam float (404) with the supporting rib or projection (406). The projection (406) is placed parallel to the flat surface of the said D shaped float (404), This provision of projection like member (406) prevents the rotation of the said foam float (404) around the drain tube (402), whereby it eliminates the possibility of closure of the drain hole (403) in the said drain tube (402).

The restriction in the entry of dust and contaminants through the drain tube of excess fuel drain system of carburetor results in increase in effectiveness of carburetion and thus enhancing the engine performance.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the claims.

We Claim:

1. An engine carburetor assembly comprising in combination

a main body defining venture throat extending there through for the movement of
air from the atmosphere toward internal combustion engine;

a throttle valve located in the main body passageway for regulating the air fuel
mixture flow; and

a float bowl located at the bottom of the main body for holding fuel wherein the
said float bowl comprises:

a drain tube to drain excess fuel;

a drain hole located towards the top end of the drain tube; and

a float coaxially mounted on the drain tube.

2. An engine carburetor assembly as claimed in claim 1, wherein the said float closes the drain hole when there is no fuel in the float bowl.

3. An engine carburetor assembly as claimed in claim 1, wherein the said float opens the drain hole when there is excess fuel in the float bowl.

4. An engine carburetor assembly as claimed in claim 1, wherein the said float is preferably of D shaped.

5. The float as claimed in claim 4, wherein the said float flat surface is supported by a projection from the bottom of the float bowl.

6. An engine carburetor assembly as claimed in claim 1, wherein the said drain
hole is made perpendicular to the projection axis.

7. An engine carburetor assembly as claimed in claim 1, wherein the said float is provided with at least two window towards the top of the float which are perpendicular to the flat surface of the float.

8. The window as claimed in claim 7, wherein the said window and the drain hole align with each other.

9. An engine carburetor assembly as claimed in claim 1, wherein the said float is preferably made up of polymer resin.

10. An engine carburetor assembly as claimed in claim 1, wherein the said drain
tube top end is closed by the top surface of the float bowl.